Special Offer! It’s time to go to Mars!
The Korolev Crater on Mars, taken by Mars Express High Resolution Stereo Camera. Credit Bjorn Schreiner/FU Berlin/DLR/ESA
The next few weeks are exciting ones for the exploration of Mars. Between now and the end of July, three robotic missions are planned to be launched towards our red neighbour. These are:
Emirates Mars Mission, from the UAE, an orbiter, due to be launched today, July 19th
Tianwen-1, from China, an orbiter, lander and rover, due to be launched 23rd July
Mars 2020, a rover called Perseverance and (get this) a helicopter, due to be launched 30th July 2020
A forth was planned, the joint ESA / Russian ExoMars / Rosalind Franklin mission, but further testing and Covid-19 have pushed this back to 2022.
But why are so many missions going to the red planet in such a short time? This relates to the geometry of planets and a bit of rocket science, as shown in the figure below:
Not to scale!
Mars orbits further away from the Sun than Earth, and there are number of trajectories that could be used to get there. This figure shows two alternatives: a short way (white line) and longer way (blue/red line). The short way might take only a few weeks but requires an awful lot of energy to both leave Earth orbit and also enter orbit around Mars and not fly on out into deep space. That energy means more rocket fuel, and that means expense and complexity in launching it into space.
The long way is called the Hohmann transfer orbit and generally requires the minimum amount of energy for a direct transfer but takes 7 -8 months. It also needs the two planets to be in the right configuration so when the spacecraft reaches the furthest point in its orbit (the apogee), Mars will be waiting for it. That means it must be launched at specific times when the relative geometry of the planets is just right - the so called launch window.
And one has opened up just now - the next won’t be until 2022.
In Martian Blood, a mission is sent to Mars that gets there a lot quicker than 8 - 9 months: partly this was because it was using more advanced (nuclear) propulsion systems than will be used by the current batch of space missions, and partly because of the urgency of the mission.
Good luck to all those preparing spacecraft for launch!
Special offer: to celebrate these launches, Martian Blood will be free for download on the Amazon web site on the 20th of July!
